This invention relates to stringed instruments and more particularly to a new and improved transducer for separately sensing the vibrational movement of a string of the stringed instrument in two mutually perpendicular planes and for supplying separate electrical signals related to the vibrational movement of the string in each of the two mutually perpendicular planes.
Transducers or pick-ups as they are commonly called have been widely employed in a variety of different electric guitars and other stringed instruments for the purpose of deriving electrical signals corresponding to the vibrational movement of the string. The electrical signals are then amplified and supplied to speakers to obtain an amplified sound over that which would be available from vibration of the string itself. A significant portion of musicians playing guitars and similar stringed instruments utilize instruments employing transducers.
The typical prior art transducer employs a pole piece of magnetically permeable material which conducts and emanates magnetic flux. The pole piece is positioned sufficiently close to the string so the vibratory movement of the string toward and away from the pole piece changes the reluctance through the air gap adjacent the pole piece. Reluctance changes cause the flux in the pole piece to change in a related manner, and the flux changes induce the electrical signals. Conventional transducer assemblies typically sense vibrational movement of the strings in a plane perpendicular to the plane collectively defined by all the strings of the instrument.
It is known that a string which is plucked or strummed will typically vibrate in a complex pattern. The center point of a plucked string may vibrate in a linear, circular, oval, figure eight or a variety of other complex patterns. Prior art transducers, however, have sensed the string movement only in a single plane, although the actual audible effect created by the vibrating string itself may contain frequencies and effects which are distinguishable from the vibrational movement of the string in that single plane. Consequently the electrical signals generated by the prior art single-sensing plane transducers may not accurately reflect the sound effect created by the vibrating string.
Certain prior art transducers have even attempted to eliminate the effects of the string vibrations in planes other than the single-sensing plane. U.S. Pat. No. 3,453,920 discloses a piezo-type bridge pick-up for a guitar. Two piezoelectric crystals are mechanically contacted with the string at a bridge to sense any string vibration. The piezoelectric crystals are mechanically oriented to sense horizontal and vertical string vibrations, although the crystals may also dampen the string movement. The piezoelectric crystals are electrically connected to electrically cancel the signals developed from the horizontal string vibration.
Prior art relating to deriving signals representative of the string vibration in two mutually perpendicular planes is disclosed in U.S. Pat. No. 4,143,575. The arrangement described in U.S. Pat. No. 4,143,575 employs a pair of radio frequency coils oriented with their axes in non-intersecting relation with each string, a signal generator for conducting radio frequency signals through each string of the stringed instrument, signal processing circuitry including an AM detector for detecting the modulation in the radio frequency signal of the string as sensed by the radio frequency coils, and an amplifier and speaker for amplifying the audio signal obtained from the AM detector. The radio frequency signal processing equipment and radio frequency coils have heretofore been regarded as necessary to detect string vibration in each of the two mutually perpendicular planes with sufficient signal separation to obtain two audibly distinguishable signals from string vibration in the two mutually perpendicular planes.
Other shortfalls and deficiencies in the development in this art may be known. In general, however, a greater appreciation for the significance of the present invention should be revealed by a more complete understanding of the previous developments in this art.